– A streams of thoughts contribution by Hayat Nasirova; co-edited by Paola Mazzoglio, Ritesh Patro and Swamini Khurana
“Mud volcano” is a generic term commonly used to describe any structure that emits water, mud, or hydrocarbons. Although mud volcanoes occur most commonly offshore, onshore mud volcanoes also exist in selected localities, generally in compressional tectonic settings (Milkov, 2000; Kopf, 2002). The petroleum bearing Caspian basin (CB) is located within the Alpine-Himalayan mobile tectonic belt, where earthquakes and intense modern earth crust movements have been observed. CB is a relic of the Tethys Ocean originating in the post-orogenic stage of regional development. It is an intermountain basin surrounded by mountain systems: Great and Lesser Caucasus, Talysh, Elburs, Kopetdag and Balkhan (Feyzullayev, 2012).
Dashli Island is one such island formed by a mud volcano. It was discovered in the 18th century by Russian sailors under Peter the Great who named it “St. Ignatius Stone”, after Ignatius of Antioch. The Dashli mud volcano emits hotbeds of polyaromatic hydrocarbons (PAHs) with continuous methane discharge as well (Remizovschi and Carpa, 2021).
Mud volcanic eruptions are important events in crustal construction. Over durations of hours to years, eruptions produce new deposits, transfer heat from Earth’s interior to the overlying air or seawater, and significantly modify the landscape and perturb local ecosystems. Mud volcanic eruptions in seas and lakes are much more difficult to detect and observe than subaerial eruptions, so comparatively little is known about them. Studies of the recent Dashli submarine eruption reveal information about its changed water and air quality, hydrological cycle, and environmental impacts.
The Southwestern region of the Caspian Sea is unique and has no equal in the world in terms of the number of mud volcanoes and their diversity and very vigorous activity (Aliev, 2014). As a result of mud volcanic activities in marine conditions, islands, banks, shoals, and underwater ridges are formed. There are about 200 underwater mud volcanoes in the Caspian Sea (Fig.1). About 120 of them belong to the Azerbaijani sector of the Caspian Sea. According to statistics, an average of 3-4 mud volcanoes erupt in the Caspian Sea every year. This is typical for Azerbaijan, about 60% of mud volcanic activities happen during the full or new moon periods (Guliev, 2004).
On July 4, 2021, at 21:51(GMT+4), an 8-minute-long strong latest volcanic eruption from the mud volcano was recorded on the Dashli island. The blaze was observed in the form of red light in the sky off the coast of Azerbaijan, even from the capital Baku, which is 74 km to the north. The flames towered 500 meters into the air. The internal structure of the mud volcano and the processes responsible for the Dashli volcanic eruption geomorphology are not known. However, it is a fact that this Dashli Island itself was formed by a past eruption. We can estimate the amount of gasses produced by Dashli mud volcano by assuming it to be continuously active, with an average methane production similar to that observed in 1920 and 1945 between the rare major eruptions. The conservative estimate is that the Dashli mud volcano produces an annual amount of at least 800 Sm3 (standard cubic meters) of gas, mainly methane. These gasses are emitted directly into the atmosphere (Martin Howland, Andrew Hill, David Stokes, 1997).
It is extremely rare to record the moment of the eruption itself. But on July 4, 2021, it was successfully using Sea Information System tools from ships, and also in the form of a thermal anomaly by state of the art radiometers installed on satellites such as Sentinel-3A satellite and Sentinel-3B satellite.
Natural outputs of petroleum hydrocarbons associated with mud volcanism in the area of Dashli Island are regularly manifested in satellite images of high spatial resolution, of both optical and radar sensors. As shown by radar observations, the area of Dashli Island increased by 2.4 times after the eruption. On satellite images, both radar and optical, mud volcanoes are identified due to the presence of films containing petroleum hydrocarbons of natural origin on the surface (Lavrova et al., 2016; Mityagina, Lavrova, 2020). The eruption was registered by the SLSTR radiometer (in the 3.5–3.9 µm channel) on the Sentinel-3B satellite as the thermal anomaly visible in Fig.3a as a black dot (high-temperature zone). At the same time, the ejection resulting from the explosion is clearly visible (white spot in the image). Ejection spacing was also recorded at 18:48 GMT by the SLSTR instrument of the Sentinel-3A satellite (Fig.3b) and 19:15 GMT by the MODIS (Moderate Resolution Imaging Spectroradiometer) satellite Terra (Fig 3c).
The radar image of July 8 shows the spread of a slick band caused by the presence of petroleum hydrocarbons, which may indicate the continued activity of mud volcanism. It should also be noted that after the explosion, the activity of the volcano continued. This is clearly seen in the data of the survey made by the satellite “Meteor-M” No. 2 (KMSS device (complex of multi-zone satellite imagery)). In the area of the eruption, massive extinction of birds and water snakes was discovered. Due to its proximity to the Caspian Sea, eruptions of the Dashli mud volcano (and of other similar mud volcanoes) have further implications with respect to water and air quality, hydrological cycle and the wider ecosystem in the area. The risk of contamination of water resources by petroleum hydrocarbons is clear, going by the thermal anomaly in the satellite images above). Mud volcanoes are also known to spew out fine sediment, and their eruption potentially affects the water currents (see increasing size of the Dashli island above) in the radius of influence of the volcanoes. Additionally, iodine, bromine, calcium, magnesium, are some of the chemicals known to be ejected from the mud volcanoes, and these may influence physico-chemical changes in the Caspian Sea. Therefore, this volcanic eruption phenomenon in the region needs to be explored and analyzed further from various hydrological aspects.
About the author:
Hayat Nasirova is geographer and teacher with a background in education. She originally completed her Bachelor’s degree in Earth Science from Azerbaijan State Pedagogical University and is currently a Master’s student in Physical Geography: Climate and Environmental Sciences at the Friedrich–Alexander University Erlangen–Nürnberg. She is an experienced science communicator, especially with respect to the intersection of science and contemporary art, having led masterclasses and workshops integrating and articulating scientific phenomena on art and canvas. She runs a series of courses called “The History of Science” and “Sci-Art”, as part of the Pint of Science festival. She can be reached on LinkedIn. Hayat has also contributed to the EGU Blogosphere in the past.
Dyan Thuras, 2021: https://www.atlasobscura.com/places/mud-volcanoes-of-azerbaijan
Mark Tingay, https://www.bbc.com/news/world-europe-57722236
Alexei Remizovschi and Rahela Carpa, 2021
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